During operation of a motor, various motor components may flex or move, causing components to rub against each other. Prolonged rubbing may cut into motor parts, causing malfunction such as shorting. Malfunction can be prevented by detecting rubbing and intervening before parts become so worn out as to be non-functional. One cause of rubbing in motors is closing up of an airgap between a rotor and a stator during certain parts of operation such as high cross flow or when the motor is operated at high torque. For example, the motor may close up due to a shaft bending under loads, the stator vibrating, among other things. Another cause of rubbing is foreign object debris that originates in the motor or is inadvertently sucked into the motor such as into a primary cooling path or space between the rotor and stator. Conventional techniques for rubbing detection are invasive, typically requiring a motor to stop operation and be taken apart.